Devonian Reef Development And Distributional Characteristics In Youjiang Basin

This paper was primarily focused on distribution and development of Devonian reef in Youjiang basin.On the guide of Sedimentology, Moderm sedimentology, Tectonics, and same other trational geology theories,and based on lots of outcrops, thin section, Drilling cores, Well logging, combining with research results of previous studies, after reasrched regional tectonic features, depositional system and anatomy of a single reef, plane distribution characteristics has been researched in this paper.Studies suggest that five depositional systems has been recognized, that is fluvial system, coastal depositional system, Carbonate platform system, shelf system and inter-platform basin system. Diversity reef is developed in the different sedimentary enviornment, pacth reefs,knoll reefs ,platform margin reefs,platform interior reefs often growed in platform system, pinnacle reefs and inter-platform basin reefs mainly developed in inter-platform basin system. our study area mainly include the threes types of reefs,platform interior reefs,platform margin reefs,inter-platform basin reefs.On the basin of dissection nine typical reef of Divonian in the study area, evolution law of Reef-Building organism in Devonian is summed up, that is the main reef-building organism is coral, the minor is stromatopora, The main reef-attached organisms is single coral, crinoidal, brachiopod shells and bivalve in the early Devonian. The main reef-building organism is cral and sromatopora. The main reef-attached organisms is dendritic Stromatopora, single Coral, brachiopod, dinosaur egg-bearing strata and crinoidal in the middle Divonian. The style of reef-building organism and reef-attached organisms in the late Devonian is similar to middle Davonian, after F F event, the main reef-building organism is microorganism such as bacteria and algae. The minor is kwai rock.On the basin of further analysis of the more of 30 reef outcrop and well drilling, the reef developed in the Davinian is divided into three reef building age.The first one is Emsian period and the main reef-building organism is coral and stromatopora. The reef is mainly distributed in east to south of Yunan and west of Guangxi and the specific location is Muli of guangnan, Qinjia of Debao, Hanshan of Longlin and other location. The second one is Givetian period and this period is the most prosperous one. The main reef-building organism is also the coral and stromatopora and the reef-attached organisms is various categories. The distribution is wide and can be divided into many eare from south to north which including Qujing, Puan, Fuyuan of Yunan,west to south of Guizhou and Longli, Dushan, Nandan and Guilin in the north of Guangxi. The third one is Fransnian period, the main reef-building organism is microorganism such as bacteria and algae. Reef in this period is mainly distributed in Guilin and Liujing of Guangxi.According to stratigraphic features, regional struture, develop charactristc of sedimentary system, and comprehensive analysis the relationship between reef building with palaeogeographic and sea-level changes., the control facters of development and distribution of reef is discussed. The development of reef in the study eara is mainly controled by tectonic position, sea-level changs, sedimentary enviornment, and reef-building organism. The distribution characteristc of reef is mainly controled by tectonic position. The growth and development or death of reef is controled by sea-level changs. The growth and development of reef is controled by sedimentary enviornment. The type of reef is controled by reef-building organism.